FIG. 7 is a schematic perspective view showing a chemical mechanical polishing (CMP) apparatus. As shown in FIG. 7, the CMP apparatus is configured to supply slurry from a nozzle 102 onto a polishing pad 101 mounted on a rotating polishing table 100, while pressing a wafer W against the polishing pad 101 to thereby polish a surface of the wafer W. The wafer W is rotated by a polishing head 105 while being pressed against a polishing surface 101a of the polishing pad 101. The surface of the wafer W is polished by a combination of a chemical action of the slurry and a mechanical action of abrasive grains contained in the slurry.
During polishing of the wafer W, as shown in FIG. 8, flow of the slurry is formed between the wafer W and the polishing pad 101 due to a pumping effect of the wafer W, because the wafer W is being rotated by the polishing head 105. Such flow of the slurry affects a pressure of the slurry applied to the surface of the wafer W. When a table surface of the polishing table 100 and a wafer holding surface of the polishing head 105 are parallel to each other, a pressure distribution of the slurry is concentric with the center O of the wafer W as shown in FIG. 9.
However, when the polishing head 105 tilts, the flow of the slurry changes, resulting in a change in the pressure distribution of the slurry as shown in FIG. 10. If the center of the pressure distribution deviates from the center O of the wafer W, the pressure of the slurry acting on the surface of the wafer W becomes uneven, thus causing uneven polishing rate of the wafer W.